Ps3 portfowarding help nat and napt nat type 2 then type 3?

on my modem i have settings for nat and napt, after a long struggle for nat type 2 on my ps3, i have just discovered that if i simply put nat to my ps3 ip address, it is type 2 but i do not get internet on my computer. if i put it to napt and porfoward the psn ports, i get nat type 3 and i can get on the internet on my computer? WTH! someone with better networking knowledge please help me! i am trying to get nat type 2 while still being able to get internet on my computer